The present invention relates to a network management system, and more particularly to a network management system for storing a plurality of alarm information in an alarm code form and managing them. The alarm information is generated from each one of the objects, which are to be managed.
Each object may be in various states. For instance, object A may be in a state in Which alarm a1 has arisen and in another state in which alarm a2 has arisen.
Conventional state management systems for managing the states of objects for each, of which a plurality of alarms may have arisen simultaneously can be broadly classified into two types: one method using bit patterns (see the JP-A-283137 (1990)) and the other method using the storage of alarm information (see JP-A-50540 (1990)).
By the method using bit patterns, a network management system manages a plurality of alarms, arising for each object, in a bit pattern form. Thus, in identifying the main cause alarm which gives rise to the true alarm among the plurality of alarms, a state management area, from a few bytes to a few dozens of bytes, for arising alarms is secured in a memory for each object, and a specific alarm is assigned for each bit in the state management area. The bit is ON when an alarm has arisen, and OFF when in a recovered (normal) state. For instance in a network consisting of objects A, B, C and D as illustrated in FIG. 2, if alarms a1 and a2 arise in object A and alarm b occurs in objects B and C, the state management area is updated as shown in FIG. 11A.
Further, every combination of alarm codes, coded expressions of alarm information indicated as messages or bit patterns, that may arise is entered in a fixed form as a bit pattern for comparison with the state management area. The entry of bit patterns should take account of the network configuration of the objects which are to be managed. Each bit pattern represents the result of identification of one main cause alarm as distinguished from effect alarms, alarms arising secondarily as consequences of the true cause of failure which is the main cause. If, upon occurrence of alarm a1, effect alarm b arises in the adjoining object but alarm a2 does not affect the adjoining object, bit patterns shown in FIG. 11B should be entered. For instance, FIG. 11B 1 indicates that "alarm a1 arising in object A affected objects B and C." Therefore, this method using bit patterns requires the addition of a new, or the modification of the existing, decision bit pattern for identifying the one main cause alarm out of a plurality of alarms every time any alarm code is added or the system structure information is updated. Furthermore, as the number of bit patterns increases acceleratedly with an increase in the variety of alarms, their maintenance takes a very long time. By the bit pattern method, the states of objects are derived by matching in a fixed period the currently existing bit patterns in the state management area with the entered bit patterns.
On the other hand, by the method using the storage of alarm information, alarm information is saved and stored in a file either as it is or in a coded form. This method has a decision logic by which, for instance if alarms a1 and a2 arise in object A and alarm b occurs in objects B and C as shown in FIG. 2, a file shown in FIG. 11C is searched with alarm a1 as key to find its combination with alarm b, and a final decision is made according to correspondence with system structure information. Even if alarm information cannot be collected from object A for some reason, if the occurrence of alarm b in objects B and C is known, the occurrence of alarm a1 in object A can be presumed. In this manner, by the method using the storage of alarm information, the state for which either alarm a1 or a2 is the main cause alarm is derived by searching the storage files.
According to the conventional state management system by the method using bit patterns, every alarm is assigned to a bit on an object-by-object basis. Therefore, in order to manage a plurality of alarms arising in the same object, all the combinations of bit patterns of both the applicable object and the affected objects should be entered, with the system structure also taken into consideration. As a consequence, there is the problem that bit patterns should be entered or altered every time the object structure is changed by the additional installation or removal of any object. There is another problem that increases in the number of objects and in the variety of alarms would invite an accelerated enlargement of the capacity of the state management area. Furthermore, there is still another problem that, when detailed information on the failure is added by a message, since the quantity of information that can be held in a bit pattern form is is limited, the added detailed information is discarded and invalidated when it is to be converted into a bit pattern.
On the other hand, according to the conventional system by the method using the storage of alarm information, an increase in alarm information would entail not only a change in decision logic but also an elongation of the searching time needed for decision. If, conversely, an attempt is made to shorten the time required for decision, the logic will become complex, resulting in a longer maintenance time. If the object structure is frequently altered, many manhours will also have to be spent on maintenance. Thus, the system by the method using the storage of alarm information also involves the problem of vulnerability to changes in logic or object structure accompanying an increase in alarm information.
The object of the present invention is to provide a network management system capable of flexibly coping with changes in alarm information or object structure by using alarm codes stored in a state management area for the state management of plural alarm information generated from one object.